Cardiac Index in Term Pregnant Women in the Sitting, Lateral, and Supine Positions

Maternal posture-physiology interactions in human pregnancy: a narrative review

There are several well-known medical conditions in which posture and gravity interact with natural history, including pregnancy. In this review, we provide a comprehensive overview of interactions between maternal posture and maternal physiology and pathophysiology at rest during pregnancy. We conducted a systematic literature search of the MEDLINE database and identified 644 studies from 1991 through 2021, inclusive, that met our inclusion criteria. We present a narrative review of the resulting literature and highlight discrepancies, research gaps, and potential clinical implications. We organize the results by organ system and, commencing with the neurological system, proceed in our synthesis generally in the craniocaudal direction, concluding with the skin. The circulatory system warranted our greatest and closest consideration-literature concerning the dynamic interplay between physiology (heart rate, stroke volume, cardiac output, blood pressure, and systemic vascular resistance), pathophysiology (e.g., hypertension in pregnancy), and postural changes provide an intricate and fascinating example of the importance of the subject of this review. Other organ systems discussed include respiratory, renal, genitourinary, gastrointestinal, abdominal, and endocrine. In addition to summarizing the existing literature on maternal posture-physiology interactions, we also point out gaps and opportunities for further research and clinical developments in this area. Overall, our review provides both insight into and relevance of maternal posture-physiology interactions vis à vis healthcare's mission to improve health and wellness during pregnancy and beyond.

Impact of maternal posture on fetal physiology in human pregnancy: a narrative review

In numerous medical conditions, including pregnancy, gravity and posture interact to impact physiology and pathophysiology. Recent investigations, for example, pertaining to maternal sleeping posture during the third trimester and possible impact on fetal growth and stillbirth risk highlight the importance and potential clinical implications of the subject. In this review, we provide an extensive discussion of the impact of maternal posture on fetal physiology from conception to the postpartum period in human pregnancy. We conducted a systematic literature search of the MEDLINE database and identified 242 studies from 1991 through 2021, inclusive, that met our inclusion criteria. Herein, we provide a synthesis of the resulting literature. In the first section of the review, we group the results by the impact of maternal posture at rest on the cervix, uterus, placenta, umbilical cord, amniotic fluid, and fetus. In the second section of the review, we address the impact on fetal-related outcomes of maternal posture during various maternal activities (e.g., sleep, work, exercise), medical procedures (e.g., fertility, imaging, surgery), and labor and birth. We present the published literature, highlight gaps and discrepancies, and suggest future research opportunities and clinical practice changes. In sum, we anticipate that this review will shed light on the impact of maternal posture on fetal physiology in a manner that lends utility to researchers and clinicians who are working to improve maternal, fetal, and child health.

Effects of Right Lateral Position on Changes of Fetal Hemodynamics in Late Pregnancy

OBJECTIVE

We aim to evaluate the effect of right lateral position on fetal hemodynamics (including umbilical artery [UA] and middle cerebral artery (MCA) blood flow-velocity waveform).

METHODS

In total, 150 low-risk singleton full-term pregnant women were included in the study from November 2021 to January 2022. Doppler flow velocity waveforms of the fetal UA and MCA tested by ultrasound were collected in gestation of 37-40 weeks. Computational analysis was performed using the one-way ANOVA test.

RESULTS

Compared with the maternal left lateral position, there was a significant increase in Doppler indices of UA-RI (P = .033), UA-S/D (P = .019) and MCA-PSV (P = .021) and a significant decrease in MCA-RI (P = .030) in the supine position group. There was no statistical significance in all Doppler indices between the left and right lateral position (P > .05). Among the Doppler indices of three different maternal positions, there was no significance in both UA-PI and MCA-PI (P > .05).

CONCLUSION

There were no significant differences on changes of the fetal hemodynamics between left and right lateral positions. Pregnant women could adopt to lie in the left or right lateral position alternately to relieve the discomfort in late pregnancy.

Perioperative Anesthetic Management of the Pregnant Patient With Congenital Heart Disease Undergoing Cardiac Intervention: A Systematic Review

Maternal congenital heart disease is increasingly prevalent, and has been associated with a significantly increased risk of maternal, obstetric, and neonatal complications. For patients with CHD who require cardiac interventions during pregnancy, there is little evidence-based guidance with regard to optimal perioperative management. The periprocedural management of pregnant patients with congenital heart disease requires extensive planning and a multidisciplinary teams-based approach. Anesthesia providers must not only be facile in the management of adult congenital heart disease, but cognizant of the normal, but significant, physiologic changes of pregnancy.

Effect of positioning on blood pressure measurement in pregnancy

Blood pressure is the key vital sign to detecting hypertensive disorders in pregnancy. The importance of taking blood pressure properly was recently underscored by the publication of updated ACC/AHA guidelines for measuring blood pressure in patients. However, the recommended position of seating with arms and back supported is not always feasible to achieve clinically, especially for inpatient women who are pregnant. Therefore, it is clinically important to understand the effects of alternative patient positioning on blood pressure measurements. We conducted a review of studies which considered patient position on the effect of blood pressure in pregnancy. This review demonstrates that clinically significant differences may occur based on patient positioning. Despite the small number of primary studies that include pregnant women, notable reductions in blood pressure measurements have been observed in the left lateral recumbent position, a common position during labor or during monitoring, in comparison to measurements taken in the supported seated position. Ultimately, these differences could affect the clinical management of patients and care should be taken to document and consider the position in which the reading was taken.

Supine hypotensive syndrome of pregnancy: A review of current knowledge

Since the first description of supine hypotensive syndrome in the 1950s, its potentially detrimental effects on otherwise healthy women during late pregnancy have become a persistent challenge in obstetric practice. Establishing a 15° left lateral tilt during labour and caesarean section is a fundamental principle of obstetric care, universally adopted and upheld by current guidelines and recommendations. Reassessment of the original landmark studies in the light of current physiological and anatomical knowledge questions adherence to this standard in clinical practice. The modern practice of providing vasopressor support during caesarean delivery under neuraxial anaesthesia appears to negate any potential negative effects of a maternal full supine position. Recent MRI studies provide evidence as to the cause of supine hypotension and the physiological effects of different maternal positions at term. This review highlights current data on the acute supine hypotensive syndrome in contrast to traditional knowledge and established practice.

Pathophysiological changes associated with sleep disordered breathing and supine sleep position in pregnancy

Sleep is a complex and active physiological process that if disrupted, can result in adverse outcomes both within and outside of pregnancy. Sleep disordered breathing (SDB) occurs in 10-32% of pregnancies. Substantial physiological changes occur during pregnancy that impact on maternal sleep, which typically deteriorates with advancing gestation. Pregnancy challenges maternal homeostatic regulation of many systems which effect maternal sleep, including the respiratory, cardiovascular, endocrine, and immune systems. SDB can result from varying degrees of airway compromise and potentially cause systemic hypoxia. The hypoxia may be acute, intermittent or chronic in nature with complications dependant on the duration and the gestation at which the insult occurs. It is unlikely that this effect is mediated by a singular mechanistic pathway but results from a complex cascade of events across multiple maternal organ systems. Regardless of the etiology, both SDB and supine sleep position are associated with a variety of obstetric and perinatal complications including, pre-eclampsia/eclampsia, gestational diabetes mellitus, cardiomyopathy, heart failure, fetal growth restriction, poor neonatal condition at birth, stillbirth and neuro-psychiatric problems in offspring. Both maternal sleep position and sleep disordered breathing are potentially modifiable or treatable factors that if addressed have the potential to improve maternal and fetal outcomes. This narrative review summarizes the maternal and placental pathophysiological aberrations associated with sleep disordered breathing and supine sleep position in pregnancy.

Managing congenital heart disease in the obstetric patient

OBJECTIVE

Cardiovascular disease is the major cause of pregnancy-related maternal mortality in the United States, and congenital heart disease (CHD) is the most common form of structural heart disease affecting women of childbearing age. Most females born with CHD will reach childbearing age and consider pregnancy. Adult CHD and maternal-fetal medicine (MFM) specialists managing women with CHD should provide preconception counseling, cardiovascular risk assessment prior to pregnancy that estimates maternal and fetal risk, management during pregnancy, and in the peripartum period and also know the potential complications and special circumstances that may occur in the post-partum period. This chapter will review the population at risk, patient risk prior to pregnancy, management during pregnancy, management in the peripartum and post-partum periods, and outline specific cardiovascular complications. The chapter will also briefly review some common or high-risk congenital cardiovascular lesions commonly encountered.

CONCLUSION

Management of patients with most forms of CHD encountered during pregnancy requires a multidisciplinary approach and careful team-based care to facilitate safe and appropriate management and pregnancy success.

Influence of the prone position on a stretcher for pregnant women on maternal and fetal hemodynamic parameters and comfort in pregnancy

OBJECTIVES:

To analyze the influence of lying in prone position on a specially designed stretcher on the maternal-fetal hemodynamic parameters and comfort of pregnant women.

METHODS:

A randomized, controlled trial with 33 pregnant women divided into 2 groups: pregnant group sequence 1 and pregnant group sequence 2. The order of positions used in sequence 1 was Fowler's position, prone position, supine position, left lateral, Fowler's position 2, supine position 2, prone position 2 and left lateral 2. The order of positions used in sequence 2 was Fowler's position, prone position, left lateral, supine position, Fowler's position 2, left lateral 2, prone position 2 and supine position 2. Each woman remained in each position for 6 minutes. For the statistical analyses, we used Wilcoxon's test for 2 paired samples when comparing the prone position with the other positions. The variables are presented in graphs showing the means and 95% confidence intervals. Trial Registration: Clinical Trial No. ISRCTN41359519.

RESULTS:

All the parameters were within the standards of normality. There were no differences between positions in terms of maternal heart rate, diastolic blood pressure, oxygen saturation and fetal heart rate. However, there were significant decreases in respiratory rate and systolic blood pressure in prone position 2 compared with left lateral 2. There was an increase in oxygen saturation in prone position compared with Fowler's position and supine position 2 in both sequences. All the women reported feeling comfortable in the prone position.

CONCLUSIONS:

The prone position was considered safe and comfortable and could be advantageous for improving oxygen saturation and reducing the systolic blood pressure and respiratory rate.

Transient fetal blood redistribution associated with maternal supine position

OBJECTIVE

To investigate whether fetal blood circulation is influenced by the maternal supine position.

METHODS

The inclusion criteria were good health, a singleton pregnancy, maternal age between 18 and 40 years, gestational age between 36 and 40 weeks, and an agreement to participate in the study. Each participant (n=20) was initially asked to adopt the left lateral position for 5 min, while fetal Doppler measurements were taken of the fetal middle cerebral artery (MCA), umbilical artery (UA), and umbilical vein (UV). Subsequently, they were asked to change to the supine position for Doppler measurements at 5 and at 10 min.

RESULTS

When a woman remained in the supine position for 5 min, there was a significant reduction in fetal MCA-pulsatility index (PI) (median 1.70 vs. 1.42, P=0.003). This reduction did not persist after 10 min (median 1.70 vs. 1.65 P=1.0). There was no significant difference between the left lateral and the supine position at 5 and at 10 min in terms of UA-PI (0.853 vs. 0.870 vs. 0.858, P=0.850), UV flow (217 vs. 242 vs. 236 mL/min, P=0.263), and normalized UV flow (72.2 vs. 80.8 vs. 78.8 mL/min/kg, P=0.271).

CONCLUSIONS

Changing maternal position from the left lateral to the supine position caused a reduction in resistance in fetal MCA and no changes in UA or UV indices. However, despite the changes in cerebral circulation which occurred at 5 min by shifting position, they did not remain for 10 min. The changes may be related to reduction in maternal oxygen saturation as there was no decrease in UV blood flow.

Management of Pregnancy in Patients With Complex Congenital Heart Disease: A Scientific Statement for Healthcare Professionals From the American Heart Association

Today, most female children born with congenital heart disease will reach childbearing age. For many women with complex congenital heart disease, carrying a pregnancy carries a moderate to high risk for both the mother and her fetus. Many such women, however, do not have access to adult congenital heart disease tertiary centers with experienced reproductive programs. Therefore, it is important that all practitioners who will be managing these women have current information not only on preconception counseling and diagnostic evaluation to determine maternal and fetal risk but also on how to manage them once they are pregnant and when to refer them to a regional center with expertise in pregnancy management.

Awareness and Aortocaval Obstruction in Obstetric Anesthesia

Awareness during general anesthesia for cesarean delivery continues to be a major problem. The key to preventing awareness is strict attention to anesthetic technique. The prevalence and implications of aortocaval compression have been firmly established. Compression of the vena cava is a real occurrence when assuming the supine position. Relief of this compression most likely does not occur until the patient is turned 30°, which is not feasible for performing cesarean delivery. Although it is still wise to tilt the patient, the benefit of this tilt may not be as great as once thought.

Cardiac output and related haemodynamics during pregnancy: a series of meta-analyses

OBJECTIVE

Cardiac output, a fundamental parameter of cardiovascular function, has consistently been shown to increase across healthy pregnancy; however, the time course and magnitude of adaptation remains equivocal within published literature. The aim of the present meta-analyses was to comprehensively describe the pattern of change in cardiac output during healthy pregnancy.

METHOD

A series of meta-analyses of previously published cardiac output data during healthy, singleton pregnancies was completed. PubMed and Scopus databases were searched for studies published between 1996 and 2014. Included studies reported absolute values during a predetermined gestational age (non-pregnant, late first trimester, early and late second trimester, early and late third trimester, early and late postpartum). Cardiac output was measured through echocardiography, impedance cardiography or inert gas rebreathing. Observational data were meta-analysed at each gestational age using a random-effects model. If reported, related haemodynamic variables were evaluated.

RESULTS

In total, 39 studies were eligible for inclusion, with pooled sample sizes ranging from 259 to 748. Cardiac output increased during pregnancy reaching its peak in the early third trimester, 1.5 L/min (31%) above non-pregnant values. The observed results from this study indicated a non-linear rise to this point. In the early postpartum, cardiac output had returned to non-pregnant values.

CONCLUSION

The present results suggest that cardiac output peaks in the early third trimester, following a non-linear pattern of adaptation; however, this must be confirmed using longitudinal studies. The findings provide new insight into the normal progression of cardiac output during pregnancy.

Effect of Lateral Tilt Angle on the Volume of the Abdominal Aorta and Inferior Vena Cava in Pregnant and Nonpregnant Women Determined by Magnetic Resonance Imaging

Background:

Left-lateral tilt position is used to reduce assumed aortocaval compression by the pregnant uterus.

Methods:

Magnetic resonance images of 10 singleton parturients at full term and 10 healthy nonpregnant women were obtained for measurement of the abdominal aorta and inferior vena cava volume between the L1–L2 disk and L3–L4 disk levels in both the supine and left-lateral tilt positions (15°, 30°, and 45°) maintained by insertion of a 1.5-m-long polyethylene foam placed under the right side of the parturient’s body.

Results:

Aortic volume did not differ significantly between parturients and nonpregnant women in the supine position (12.7 ± 2.0 vs.12.6 ± 2.1 ml, mean ± SD; mean difference, –0.1; 95% confidence interval [CI], −2.0 to 1.9; P = 0.95). Inferior vena cava volume in the supine position was significantly lower in parturients than in nonpregnant women (3.2 ± 3.4 vs.17.5 ± 7.8 ml; mean difference, 14.3; 95% CI, 8.3–20.2; P < 0.001). Aortic volume in parturients did not differ among left-lateral tilt positions. Inferior vena cava volume in the parturients was not increased at 15° (3.0 ± 2.1 ml; mean difference, −0.2; 95% CI, −1.5 to 1.2; P > 0.99), but was significantly increased at 30° (11.5 ± 8.6 ml; mean difference, 8.3; 95% CI, 2.3–14.2; P = 0.009) and 45° (10.9 ± 6.8 ml; mean difference, 7.7; 95% CI, 2.2–13.1; P = 0.015).

Conclusions:

In parturients, the aorta was not compressed, and a 15° left-lateral tilt position did not effectively reduce inferior vena cava compression.

The rapid sequence spinal for category 1 caesarean section: anaesthetic trainee knowledge and practice

Rapid sequence induction of general anaesthesia (GA) is the fastest anaesthetic technique in a category-1 caesarean section (C1CS) for foetal distress. Recently rapid sequence spinal anaesthesia (RSS) has been explored as a technique to avoid the potential risks of GA in such cases. Out of hours, trainee anaesthetists are often required to provide anaesthesia for these emergencies. We surveyed their practices when performing a RSS. The aim of a RSS is to rapidly and safely achieve anaesthesia for C1CS, while optimising foetal oxygenation and preparing for possible GA. It requires anaesthetic skill, team work and communication. Many trainees understood the principles of the RSS, however, a significant number did not. Practice varied widely and no trainee had received any formal RSS training. Training for junior anaesthetists and those working in obstetric theatres, in the conduct of the RSS is crucial, to ensure safe practice, avoid delays in delivery and safely avoid the risks associated with GA in the C1CS.

USCOM-window to the circulation: utility of supra-sternal Doppler in an elderly anaesthetized patient for a robotic cystectomy

Supra-sternal Doppler (USCOM Ltd., Sydney, Australia) can be used during anaesthesia to measure cardiac output (CO) and related flow parameters. However, before the USCOM can be used routinely, its utility and limitations need to be fully understood and critical information about its use disseminated. In "Window to the Circulation" we use the example of an elderly man undergoing major urological robotic surgery to highlight the utility and limitations of intra-operative USCOM use. USCOM readings were verified against oesophageal Doppler. Despite the lack of major blood loss (<500 ml in 8-h), significant changes in haemodynamics were recorded. CO ranged from 3.2 to 8.3 l/min. The quality of USCOM scans and reliability of data was initially poor, but improved as CO increased as surgery progressed. When USCOM scans became acceptable the correlation with oesophageal Doppler was R(2) = 8.0 (p < 0.001). Several characteristic features of the supra-sternal Doppler scans were identified: Aortic and pulmonary flow waves, valve closure, E and A waves, false A-wave and aberrant arterial flow patterns. Their identification helped with identifying the main flow signal across the aortic valve. The USCOM has the potential to monitor changes in CO and related flow parameters intra-operatively and thus help the anaesthetist to more fully understand the patient's haemodynamics. However, achieving a good quality scan is important as it improves the reliability of USCOM data. The supra-sternal route is rich in flow signals and identifying the aortic valve signal is paramount. Recognizing the other characteristic waveforms in the signal helps greatly.